A stove which is powerful, heats up quickly and evenly is a kitchen essential, whether for those trying to eat healthy or who are keen in culinary arts. In recent years, many consumers opt for induction cookers because they are easy to clean and do not excessively heat up the kitchen. The Consumer Council tested 13 models of double-hob and flexi zone induction cookers and found that the heat control of 2 models was unsatisfactory when both hobs were turned on, and cooking oil could not be heated up to a specified temperature even after 45 minutes. Heat distribution of 6 models was not uniform, which might result in different degrees of doneness in the food. Nearly 70% of the models also failed to meet the International Standard IEC 60350-2 on low power control, resulting in inferior low heat cooking performances. Regarding energy efficiency, the calculated grading of 5 models based on their test performance was found to be one grade lower than its labelling; and 1 model was found to have unsatisfactory standby energy consumption, causing its calculated energy efficiency grading to be the lowest Grade 5, not matching its labelled Grade 2. These test results have been forwarded to the Electrical and Mechanical Services Department (EMSD) for follow up. The Council calls on manufacturers to improve quality control and reminds consumers to consider both performance and energy efficiency when purchasing an induction cooker, and select a model that offers convenient cooking experiences while saving energy to practise sustainable consumption.
The 13 models tested had rated input power from 2,800 watts to 5,200 watts, and ranged from $3,680 to $21,300 in price. 3 of them were newer “Flexi Zone” models with a function of combining 2 heating zones to form a larger cooking area. Test items included cooking performance, energy saving performance, and safety, etc.
Some Models Failed to Heat Cooking Oil Sufficiently Within 45 Minutes with Both Hobs On
Except for 1 model with separate power plug for each hob, all models tested were powered by a single supply line with shared wattage between its two hobs. Whether heat was sufficient and appropriately distributed when both hobs were turned on would affect the cooking time and the ultimate outcome. Tests simulated a daily cooking situation where both hobs were turned on simultaneously, with the main hob heating cooking oil at its highest power setting, while the other hob was heating water to boiling point then lowered to maintain at simmering. To compare the heating up speed when both hobs were turned on, the main hob was required to heat up the cooking oil to 180°C within 45 minutes, and depending on the size of the hob, fry 200g to 500g of frozen potato chips for 4 to 7 minutes. 2 models failed to complete the test and could only heat the cooking oil to above 170°C but failing to reach 180°C within the time limit, reflecting room for improvement in terms of heat control. Another model had a slower heating speed, taking nearly 40 minutes to reach 180°C, leaving just enough time to fry a single portion of potato chips. The remaining 10 models reached the required temperature within 13.7 to 25.3 minutes and could fry 1 to 3 portions of potato chips within the test time, quite a satisfactory performance.
Uneven Heat Distribution May Result in Inconsistent Doneness
Apart from sufficient power to heat quickly, the evenness of heat distribution of an induction cooker also affects cooking results. Tests simulated cooking crêpe in a pan, by heating up batter on a circular steel plate at a standard prescribed power setting until it reached a specified shade of brown. Results for 5 models showed the centre of the cooked crêpe was darker than the edge, indicating that heat was not evenly distributed. 1 model turned off automatically during the test when it detected overtemperature on the hob surface and triggered its built-in overheating protective device, and the centre of the cooked crêpe was also darker in colour than the edge before the cutoff. As for the 3 flexi zone models, the crêpe cooked between the 2 hobs in flexi zone mode generally had a lighter-coloured centre, while the two ends were darker. This may be due to the fact that the centre of the cooking area was in between 2 sets of coils, and heat needed to be transferred to the centre through the two ends of the steel plate, causing uneven heat distribution across the whole cooking area. In addition, extra temperature distribution tests were conducted on the flexi zone models using longer cookware, and results showed that heat was more concentrated at the front and rear areas in flexi zone mode.
Nearly 70% Models Did Not Meet the Standard Requirement of “Low Heat” Cooking
Soup or stewed dishes need to be cooked at low heat for longer periods to achieve the best results. Tests simulated melting chocolate by heating oil at low power setting, during which models were assessed against the 3 criteria of international standard for low power control: the temperature of oil should not exceed 53°C within the initial 18 minutes of heating; it should reach at least 40°C within 30 minutes; and the highest temperature should not exceed 75°C. Most models heated up the oil too rapidly at the beginning, with only 4 models being able to control the oil temperature appropriately as per the standard requirements, while the rest were unable to keep the oil temperature at 53°C or below in the first 18 minutes, thus failing to meet the standard’s requirement for low power control.
Deduced Energy Efficiency Grading of 6 Models Inconsistent with Labelling
While cooking performance of an induction cooker is important, consumers should also pay heed to the energy saving performance. Tests found that the standby power consumption (minimum power consumption when not in operation) varied considerably among models, ranging from 0.13 watts to 2.28 watts. According to the requirements of the EMSD’s Mandatory Energy Efficiency Labelling Scheme (MEELS), induction cookers with 2 heating units whose standby power consumption exceeding 2 watts can only be rated at the lowest energy efficiency grading of 5. In the “Both Hobs On” test, the model with the fastest heating speed for oil was found to consume over 2 watts on standby, thus its energy efficiency grading based on test results would be Grade 5, which did not meet its labelled grading of 2. None of the remaining 12 models measured a standby power consumption exceeding 2 watts.
The energy efficiency grading was also calculated based on the measured heating efficiency. The test results of the 3 flexi zone models were not to be used to deduce energy efficiency grading because the claimed power when operating at the maximum power boost mode was outside the scope of the test standard GB 21456. Among the remaining models, 5 were found to have an energy efficiency grading one level lower than indicated on the energy label. Under MEELS, if the heating efficiency test result is slightly lower than that submitted in the application for energy efficiency labelling, it may lead to discrepancy in their energy efficiency grading. This reflects the importance of quality control by manufacturers to ensure products available to consumers perform the same as the samples submitted in the application for the MEELS. The test results have been forwarded to the EMSD for follow-up.
All Models Passed Safety Test with 5 Missing Standard Warning Messages
The safety of induction cookers is also of utmost importance to consumers. All models passed many of the safety tests, including impact to hob surface, insulation strength and distance, heat and fire resistance of plastic materials, etc. However, 5 models were missing certain warnings required by the standard, among which 1 model had a rated voltage on the label different from that stated in the instruction manual. The Council urges the manufacturer to revise promptly to avoid confusing consumers.
Furthermore, all agents offered product warranty periods ranging from 1 year to a maximum of 5 years, and most of them (9 agents) provided warranty renewal service at an annual fee from $480 to $1,580. However, consumers should be aware that renewal of warranty does not mean all maintenance fees will be waived, for example whether transportation costs, maintenance labour, or spare parts, are included. In view of the fact that comprehensive and affordable after-sales maintenance services could help prolong product lifespan, the Council urges agents to extend warranty periods and provide more affordable warranty renewal and maintenance service charges in support of sustainable consumption.
To cook well and safely, consumers can follow these tips when purchasing and using induction cookers:
- Induction cookers generally have a higher rated power than other electrical appliances, thus an individual power source should be used instead of sharing the same outlet with other high-wattage appliances;
- Read product manuals carefully before use to fully understand instructions and recommendations. Also, choose right-sized cookware compatible with induction cookers to ensure the best heating results and avoid wasting energy;
- Before switching on the cooker, check the hob surface for cracks or damages. If cracks are found on the hob surface, stop using immediately and contact the agent for repair or replacement;
- Do not switch off the power immediately after cooking. Internal fans in most models continue to run after use to help dissipate heat from the base of the cooker and cool down the control panel. Waiting for a while before switching off the power could prevent damage to internal components caused by excessive heat accumulation while helping to prolong product life.
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